This invention relates to a recording and/or reproducing device represented by DLT (digital linear tape) or LTO (linear tape open) and, in particular, to a guide roller for guiding a tape and a method of manufacturing it.
Recording and/or reproducing devices of the type described are developed for use in back-up ones of computer systems and various types of the recording and/or reproducing devices have been proposed in prior art. Such a recording and/or reproducing device serving as the LTO is disclosed, for example, in U.S. Pat. No. 6,322,014 issued to Robert Nemeth.
The recording and/or reproducing device may be also a tape drive in which a cartridge having a single reel (a supply reel) can be installed. The cartridge may be also called a cassette. The recording and/or reproducing device contains a take-up reel therein. When the cartridge is installed in the recording and/or reproducing device, a magnetic tape (which will be also referred to “tape” merely) is pulled out of the cartridge and then is wound by the take-up reel through a guide assembly. The guide assembly is for guiding the tape pulled out of the cartridge in a magnetic head. The guide assembly comprises a plurality of guide rollers each of which uses bearings. The magnetic head exchanges information between the tape and the magnetic head. In addition, the take-up reel is rotationally drivable by means of a real motor.
In the manner which is described above, provided in the tape drive, the guide roller is guiding the tape pulled out of the cartridge in the magnetic head. The guide roller is rotatably supported on a roller shaft mounted on a chassis of the tape drive. The roller shaft includes a shaft portion of a substantially solid cylindrical shape. Such a roller shaft is disclosed, for example, in U.S. Pat. No. 6,634,535 issued to Naoki Tatsumi et al.
More specifically, the guide roller includes a roller portion and a pair of bearings for rotatably supporting the roller portion on the shaft portion of the roller shaft. Such a guide roller is disclosed, for example, in United States Patent Application Publication No. 2004/0222327 A1. The guide roller is called a first conventional guide roller. The first conventional guide roller will later be described in detail in conjunction with FIGS. 1 through 4.
A different guide roller is disclosed, for example, in Japanese Unexamined Patent Application Publication No. Hei 9-22067 or JP-A 9-22067. In the different guide roller disclosed in JP-A 9-22067, a cylindrical-shaped roller portion and a pair of disk-shaped annular flanges are separately constituted and the pair of disk-shaped annular flanges is fitted in an outer surface of the cylindrical-shaped roller portion at opposite end sides. JP-A 9-22067 also discloses the guide roller in which each flange is made of material having hardness firmer than that of the roller portion. The guide roller is called a second conventional guide roller. The second conventional guide roller will also later be described in detail in conjunction with FIGS. 5 to 8.
Incidentally, in the tape drive, as methods of realizing a large capacity, the following methods are adopted: to increase head channels, to lengthen the tape by thinning a thickness of the tape to be used, to increase a transport rate by becoming fast a tape traveling speed, or the like. However, to thin the thickness of the tape and to increase the tape traveling speed are disadvantageous in that both edges of the tape mar the flanges of the guide roller. It results in adversely affect traveling of the tape.
In order to resolve such problems, it is carried out by coating, with a material having high hardness such as titanium, ceramics, DLC (diamond-like carbon), or the like, a surface of the roller portion in the first conventional guide roller or a surface of the flanges in the second conventional guide roller. However, to apply the above-mentioned particular coating to the surface is disadvantageous in that the guide roller increases in cost.
Particularly, in a case where the roller flanges are integrally formed in the roller portion as the first conventional guide roller, the particular coating further increases in cost because the coating is applied to all of the surface of the roller portion.
On the other hand, in order to resolve the above-mentioned problems, it may be considered that only the flanges are made of a material firmer than that of the roller portion in the second conventional guide roller. However, another problem may be encountered in making the flanges of the firm material. This is because the flanges crack on press-fitting the pair of flanges in a pair of outer peripheral step parts at the both ends of a roller outer peripheral surface of the roller portion. In order to resolve the problem on press-fitting the flanges, it may be considered that it is designed so that the diameter of the outer peripheral step part is substantially equal to the inner diameter of the flange and the pair of flanges is coupled by means of an adhesive agent with the outer peripheral step parts at both sides of the roller outer peripheral surface of the roller portion. However, with the structure of the second conventional guide roller, it is disadvantageous in that the adhesive agent leaks on the roller outer peripheral surface of the roller portion.